1. Field of the Invention
The present invention relates to an ink-jet head device using a piezoelectric (PZT) actuator.
2. Description of the Related Art
Existing types of ink-jet printing methods used by drop on-demand systems include an electro-thermal transduction method and an electro-mechanical transduction method using a piezoelectric body.
In an electro-thermal transduction method, a heat source generates bubbles in ink, and the force of the bubbles discharges the ink. Thus, the performance of discharge depends on the ingredients of ink.
In an electro-mechanical transduction method using a piezoelectric body, discharge of ink can be achieved using a volume change caused by the deformation of a piezoelectric body. Thus, this method has few restrictions on the type of ink used compared to the electro-thermal transduction method. In addition, an ink-jet head device adopting this method is durable.
An ink-jet head device using a piezoelectric body is roughly made up of a chamber in which ink supplied from an ink supplier is contained, a piezoelectric actuator for changing the volume of the chamber to drive ink to be ejected, a nozzle having ink discharge holes, and driving electrodes.
The ink-jet head devices using a piezoelectric body are roughly classified into three categories: a device using a bending method, a device using a pushing method, and a device using a shear deformation method.
European Patent No. 0864425A1, for example, discloses a bending-type ink-jet head device. This bending-type ink-jet head device has a structure in which a piezoelectric body deformed by voltage is formed on a vibrating plate. In this bending-type ink-jet head device, the vibrating plate is also bent when the piezoelectric body is bent, because of the structural characteristics of the vibrating plate and the piezoelectric body. This action causes a volume change of an ink chamber which adjoins to the vibrating plate, and a change in the inside pressure of the ink chamber. A change in the volume of the chamber is required to discharge the ink, and the pressure of the chamber is needed to control the discharge performance of the ink drop. This bending-type ink-jet head device having such a structure has a trade-off between the volume change of the chamber and the pressure thereof, resulting in a limit in designing.
A pushing-type ink-jet head device is disclosed in U.S. Pat. No. 5,424,769, for example. In this device, pushing a vibrating plate using the deformation of a piezoelectric body changes the volume of a chamber. In this structure, when the vibrating plate is reduced in size to obtain a high resolution, it must be greatly deformed in order to obtain a change in the volume of the chamber.
This large deformation exerts excessive stress on the vibrating plate, often causing the vibrating plate to fail.
In a device disclosed in U.S. Pat. No. 4,395,719, for example, a piezoelectric body is designed in a tube structure, and the interior space of the tube-typed piezoelectric body is directly used as a chamber, so that a vibrating plate generates no problems. However, this device must use a flexible rubber piezoelectric body. In this case, the chamber is easily deformed, but its performance is degraded for lack of a force to discharge ink.
In order to solve the aforementioned problems, it is a feature of an embodiment of the present invention to provide an ink-jet head device using a piezoelectric actuator, which has an increased ink discharge capability.
It is another feature of an embodiment of the present invention to provide an ink-jet head device using a piezoelectric actuator, which has a high ink discharge capability even at a low voltage.
In an effort to satisfy these and other features of the embodiments of the present invention there is provided an ink-jet head device using a stacked piezoelectric actuator, including: a nozzle plate on which at least one nozzle is formed; a manifold portion having a restrictor plate on which at least one restrictor is formed; a plurality of piezoelectric bodies stacked in multiple layers and interposed between the nozzle plate and the manifold portion to form a chamber for containing ink, each of the piezoelectric bodies having a cavity at the center; common electrodes and driving electrodes alternately interposed one by one between adjacent piezoelectric bodies; a common lead line and a driving line electrically connected to the plurality of the common electrodes and the plurality of driving electrodes, respectively, for supplying a voltage to the plurality of piezoelectric bodies to cause deformation thereof; and a medium interposed at least between the restrictor plate and a piezoelectric body adjacent to the restrictor plate, and between the nozzle plate and a piezoelectric body adjacent to the nozzle plate, the medium deformed corresponding to deformation of the piezoelectric bodies.
In an additional effort to achieve the above features of an embodiment of the present invention there is provided an ink-jet head device using a stacked piezoelectric actuator, including: a nozzle plate on which at least one nozzle is formed; a manifold portion having a restrictor plate on which at least one restrictor is formed; a piezoelectric body structure interposed between the nozzle plate and the manifold portion, in which cylindrical piezoelectric bodies are stacked, and a chamber for containing ink is provided; common electrodes and driving electrodes alternately interposed one by one between adjacent piezoelectric bodies; a common lead line and a driving line electrically connected to the plurality of the common electrodes and the plurality of driving electrodes, respectively, for supplying a voltage to the plurality of piezoelectric bodies to cause deformation thereof; and a medium interposed between the restrictor plate and one end of the piezoelectric body structure adjacent to the restrictor plate, and between the nozzle plate and the other end of the piezoelectric body structure adjacent to the nozzle plate, the medium deformed corresponding to deformation of the piezoelectric bodies.
In a further effort to achieve the above features of an embodiment of the present invention there is provided an ink-jet head device using a stacked piezoelectric actuator, including: a nozzle plate on which at least one nozzle is formed; a manifold portion having a restrictor plate on which at least one restrictor is formed; a cylindrical medium which is installed between the nozzle plate and the manifold portion, and provides a chamber for containing ink; a piezoelectric body structure installed around the cylindrical medium and separated from the nozzle plate and the manifold portion, in which cylindrical piezoelectric bodies are stacked in multiple layers; common electrodes and driving electrodes alternately interposed one by one between adjacent piezoelectric bodies; and a common lead line and a driving line electrically connected to the plurality of the common electrodes and the plurality of driving electrodes, respectively, for supplying a voltage to the plurality of piezoelectric bodies to cause deformation thereof.
These and other features of the embodiments of the present invention will be readily apparent to those skilled in the art upon review of the detailed description that follows.